With the rapid development of packet service, the design of future communication network is focusing on optimizing packet service, especially IP service. Therefore, it is vital to enhance service grooming capability and improve the efficiency of service transmission. Currently, a grooming method mainly includes the following electrical cross connection or optical cross connection on a wavelength level basis, such as Reconfiguration Optical Add/Drop Multiplexing (ROADM), can selectively transfer upstream/downstream local service and carry out transmission based on a certain wavelength while transmission of other wavelengths is not affected.
The existing ROADM includes ROADM based on Wavelength Selected Switch (WSS). The structure of such ROADM is illustrated in FIG. 1. FIG. 1 illustrates a 4 dimensional ROADM system constituted by 8 WSS devices, with two loops of services invoking each other. There are various approaches to implement WSS. The most popular one is Micro-Electro Mechanical System (MEMS) technique. The WSS-based ROADM operates in the following way. A multi-wavelength optical signal is de-multiplexed by a grating device into a plurality of optical signals with different single wavelengths. After optical signals with different single wavelengths are amplified and dispersion-compensated, they were focused on different MEMS lenses. By controlling the reflection angle of the MEMS lenses, optical signals with different single wavelengths can be reflected at different output ports. Each output port employs the grating device to multiplex these single-wavelength optical signals into a multi-wavelength optical signal. Since each MEMS device is controlled independently, configuring an optical signal with arbitrary wavelength to an arbitrary output port can be achieved. Moreover, each output port of WSS may also be able to transfer upstream/downstream local services.
Inventors of the present invention discover that the existing ROADM has the following defects. The issues of light dispersion and light power loss cannot be addressed thoroughly. Especially, for a network with multi-dimensional nodes, the light dispersion and light power loss problem is particularly severe, and the light noise accumulation is also considerable. Moreover, the existing ROADM cannot adequately monitor the light signal-to-noise ratio, which affects the management of light signal-to-noise ratio. The existing ROADM also fails to monitor wavelength in real time, which affects the monitoring of optical wavelength from port to port. Also, the existing ROADM cannot address the wavelength conflicts and does not support broadcast or multicast of the service. Further, the existing ROADM employs optical devices which are rather expensive and may not be commercialized at present.